1. Field of the Invention
The present invention relates to a method and apparatus for measuring the height, width and length of articles and, in particular, to measuring electronic components such as ceramic chip carriers (packages) using a non-contact measuring device employing laser beams and an air/slide for moving the article along a defined path which method and apparatus operate at high measuring speeds, measurement accuracy and precision.
2. Description of Related Art
The dimensional measurement of articles is an important method in a number of industrial areas ranging from the automobile industry to the electronics industry. Self-contained off-line and on-line measurement systems are used for industrial quality control and operations applications and, for convenience, the following description will be directed to the electronics industry and in particular, to the measurement of electronic components such as the ceramic chip carriers used for multi-chip modules (MCM's), single chip modules (SCM's), etc. which are employed in a wide variety of electronic devices such as computers, televisions and the like.
In one application, a chip is electrically connected to a substrate such as a card, a board, another chip or any other part to which an electrical connection is required. One particular application concerns ceramic chip carriers which carriers are required to have a high degree of dimensional precision and accuracy. The chip carriers are measured in at least the x and y dimensions and preferably in all three x-y-z dimensions. In general and for consistency herein, the x dimension refers to the width, the y dimension to the length and the z dimension to the height of the article being measured. In addition to the accuracy required in the dimensional measuring process, it is also important that the measurements be performed in a relatively short period of time and that the method and apparatus used be both cost effective and reliable.
The present method for measuring ceramic chip carriers and other such articles uses an optical pattern recognition coordinate measurement device such as the View 1220 made by View Engineering Inc. of Simi Valley, Calif. The View 1220 is a self-contained off-line visual inspection and measurement system intended for industrial quality control applications. The View 1220 installation consists of a Data Gathering Unit (DGU) and a Monitor and Disk Drive Assembly (MDDA).
The DGU is composed of a granite table and arch to which are attached a precision stage, a CCD video camera and associated positioning systems. The DGU contains all the necessary imaging processing electronics and computer hardware. Recirculating ball bearings are used on x and y axes to prevent bounce in vibrating environments. A brochure entitled "View 1220" describes the system provides technical information and specifications.
These type devices operate in general by moving a camera to specified measurement locations and then using image processing software and camera position information to make measurements.
These type devices are relatively expensive and slow however, and can cause damage to the carriers or parts being measured due to contact of the carrier and the fixturing devices of the measuring instrument.
Laser scan micrometers are used to dimensionally measure articles such as wire, pressure hose, roller gaps, shafts for out of roundness, tape width and the like. These devices utilize high speed scanning beams which beams are blocked by the part being measured in their path, producing shadowed and non-shadowed sections. Basically, the measured result is displayed as an average value of measurements obtained by repeatedly scanning the object over a specified time interval. These devices can also measure a part in two orthogonal directions with a single measuring unit. Such laser scan micrometers are made by Mitutoyo and different measurement units and technical details are shown in a brochure entitled "Mitutoyo, Measuring Instruments, Catalog No. 300".
There still exists a need however, for measuring articles and parts continuously and effectively with a high degree of precision and accuracy and bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method for measuring articles, particularly electronic component articles such as ceramic chip carriers, in their x-y dimensions and preferably in their x-y-z dimensions using a high speed and cost effective measuring apparatus.
Another object of the invention is to provide an apparatus or device for measuring ceramic chip carriers and other articles in their x-y dimension and preferably in their x-y-z dimensions.
Other objects and advantages of the present invention will be readily apparent from the following description.